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Snakes and other Pets

Frank LoVecchio, DO, MPH, FACEPCo-Medical Director, Banner Good Samaritan Poison Center

Maricopa Medical Center, Research Director and Vice-ChairmanDepartment of Emergency Medicine

Phoenix, AZ

Case: A new antidote for an old problem

• A 30 year old man is envenomated by a rattlesnake.

• He has no history or asthma and takes no meds

• He has no allergies

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Tongue Bites

24 hours

RULE ONE:PLEASE DON’T KISS SNAKES

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Penetrating Ocular Injury Caused by Venomous Snakebite Chien-Chung Chen et alAJOM

RULE TWO:PLEASE DON’T HANDLE DEAD SNAKES

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CroFabTM Dose

NoAdminister Additional 4 - 6 Vials of CroFab (TM)

Initial Control Achieved?

Establish Initial ControlBy Administering 4-6 Vials of CroFab(TM)

Over 1 Hour

Patient with Indication forCroFab(TM) Administration

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VIPERIDAE ELAPIDAE COLUBRIDAE HYDROPHIDAE ATRACTASPIDIDAE

Families of Poisonous Snakes

mobile, front fangs

fixed, front fangs

fixed, rear fangs

fixed, front fangs

rear/lateral – direct-ed front fangs

US: Thousands of snake bites occur annually

Hundreds in Arizona

< 10 deaths per year

5 million snake bites

125,000 deaths

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Families of Venomous Snakes

• Viperidae

• Elapidae

• Hydrophiidae

• Atractaspididae

• Colubridae

CrotalinaeViperinae

subfamilies

(coral snakes)

Crotalinae• New world or ‘pit’

vipers• Front, mobile fangs• Triangular shaped

head• Heat sensing pits

• >95% venomous bites in US

US Pit Vipers

CottonmouthCopperhead

Rattlesnake

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MojaveWestern diamondback(C atrox) (C scutulatus)

Arizona Rattlesnakes

Speckled Rattlesnake Northern Blacktail Rattlesnake

Tiger Rattlesnake(C tigris)

(C mitchellii) (C molossus)

Massasauga(Sistrurus catenatus)

Sidewinder(C cerastes)

Ridgenose rattlesnake Rock rattlesnake(C lepidus)

Twin-spotted rattlesnake(C pricei)

(C willardi)

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Hopi Rattlesnake

Western Rattlesnake

Grand Canyon Rattlesnake

(C viridis)Arizona Black Rattlesnake

Who are the victims?

Unlucky

unintelligent

Leg bites

Hand bites

About 60% of all bites illegitimate

Illegitimate Bitesmale 97.9%female 2.1%alcohol 56.0%

Legitimate Bitesmale 72%female 28%alcohol 16%

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Lower extremities-39.3%

Upper extremities-60.2%

Other-0.4%

Location of Rattlesnake Bites

“Mighty Fighting Sun of Love and Ecstasy”

VIPERIDAE

Crotalinae Viperinaepit vipersnew world vipers

old world vipers

Crotalus Sistrurus Agkistrodon

rattlesnakes cotton mouthscopperheads

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Legitimacy of Snakebite• Legitimate Bite

– did not recognize encounter with snake before being bitten

– recognized encounter and immediately attempted to move away, but was bitten anyway

• Illegitimate Bite– recognized encounter with

snake, but did not try to immediately move away

– pet snakes, moving snakes, killing snakes, kissing snakes, playing with snakes, feeding snakes

Demographics and Characteristics236 patients

Populationmale 81%female 19%children 22%

Locationupper extremity 60.2%lower extremity 39.4%other 0.4%

Edema After Snakebite

• Swelling looks very scary

• Long, linear incisions on envenomated extremity would decrease tissue pressure and might “restore” blood flow

• Tissue necrosis would then be prevented

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Rattlesnake Bite

noswelling

mildswelling

severeswelling

noinsurance

excellentinsurance

long linearincisions

Compartment Syndrome• Other management options

• Antivenom• Antivenom and mannitol

Venom

• Enzymes– Proteolytic– Thrombin-like– Hyaluronidase– Phospholipase A2

– Many others….

• Non-enzymatic proteins

• Metals • Lipids• Biogenic amines• Amino acids

NecrosisHematologic toxicityTissue

damageDisrupts cell membranes

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Tissue Hypertension

• Tissue hypertension quite exceptional despite edema

• Fasciotomies and SQ decompression do not prevent myonecrosis in animals receiving IM or SQ venom injections

• Noninvasive vascular studies demonstrate increased blood flow in envenomated extremities in most all patients

venom

edema and ischemia

inflammation

VMPs

ProTNFa

TNFa HMP activation

ECM protein degradation

NECROSIS

+ +

ANTIVENOM

only effective if antivenom infused within a few minutes of envenomation

Local Tissue Effects• Puncture wounds / scratches / lacs

• Swelling – Mild to massive– Progression

varies

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Local Tissue Effects• Hemorrhagic bulla (blebs)

• Local necrosis– Tissue loss– Amputation

• VMPs and other digestive enzymes

Blebs

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Blebs

Myotoxicity

• Digestive enzymes and metalloproteinases

• More specific myotoxins– myotoxin a and similar proteins

• prairie rattlesnake (C. viridis viridis)• midget faded rattlesnake (C. viridis concolor)• common in other Crotalus and Sistrurus

species

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Myotoxicity

venom

direct injection into muscle produces local myonecrosis

digestive enzymesmetalloproteinasesmyotoxins

venom

subcutaneous

systemicrhabdomyolysis

digestive enzymesmetalloproteinasesmyotoxins

systemicabsorption

Coagulopathy

• About 60% of victims develop coagulopathy

• Hypofibrinogenemia with prolonged clotting times by far the most common

Coagulopathy

clotting cascade

prothrombin thrombin

fibrinogen fibrin chain

inactive XIII

active XIII

fibrinopeptide A & B

Normal Coagulation

cross linking

inhibited by heparin

fibrin mesh

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Coagulopathy

thrombin-like enzymes

fibrinogenpoorly-constructed fibrin chain

fibrinopeptide A

Crotalinae Thrombin-like Enzymes

fibrinopeptide B OR

only split FP-A or FP-B from fibrinogen

Coagulopathy

thrombin-like enzymes

fibrinogenpoorly constructed fibrin chain

fibrinopeptide A

Crotalinae Thrombin-like Enzymes

fibrinopeptide B OR

inactive XIII

active XIII

only split FP-A or FP-B from fibrinogen

doesn’t activate factor XIII

fibrin mesh

Coagulopathy

thrombin-like enzymes

fibrinogenpoorly constructed fibrin chain

fibrinopeptide A

Crotalinae Thrombin-like Enzymes

fibrinopeptide B OR

inactive XIII

active XIII

only split FP-A or FP-B from fibrinogen

doesn’t activate factor XIII

fibrin mesh

not inhibited by heparin

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Hypofibrinogenemia

• Two main mechanisms1.Thrombin-like enzymes2.Fibrinolysis/Fibrinogenolysis

• degrade fibrinogen• degrade fibrin

FibrinolysisFibrinogenolysis

fibrinogen fibrin chaincross linking

fibrin mesh

enzymatic degradation of fibrinogen and fibrin

degradation products

Benign Defibrination

• hypofibrinogenemia and prolonged clotting times

• no abnormal intravascular coagulation

• significant bleeding unusual in absence of thrombocytopenia or trauma

• occasional blood loss into envenomated extremity requires transfusion

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Venom-Induced Thrombocytopenia

• About 30% of victims experience thrombocytopenia

• Nadir in untreated patients commonly between 72 and 96 hours

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Anaphylaxis

• Rare• IgE mediated• Pre-sensitized to crotalids

– Previous bites– Dermal exposure– Ingestion of rattlesnake meat?

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Case• 25 yo man presents 25 min following RSB to

hand

• SBP = 68/28 mmHg, intoxicated

• 20 min later develops tongue, facial, and neck edema with airway compromise

Case

• IVF, epinephrine (SBP 90 x 2 hr)• Difficult intubation (sat>90%)

• Minimal swelling• Mild coagulopathy• Treated with AV

• Rhabdomyolysis(CPK = 120,000)

• Renal failure• Hemodialysis

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Outcome• Complicated course

– Recurrent large bowel enterocutaneous fistulas

– Sepsis– Malnutrition– Died one year later in rehab facility

• History of capturing and cooking RS

Respiratory Failure• Patient presents following RSB with muscle

weakness and diplopia.

• Rapidly progresses to hypoventilation and respiratory failure.

• Despite antivenom treatment, patient requires intubation.

DIC• Extremely uncommon• Labs similar to

venom-induced thrombocytopenia and defibrination, with additional findings of:– Hemolysis– Red cell fragmentation– Organ infarction– Diffuse bleeding

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ED Management• IV fluids• Pain control • Measure

circumference• Neurovascular

checks• Elevate extremity

Antivenom?

Indications for Antivenom

• Rapid progression of swelling• Significant coagulopathy or

thrombocytopenia• Neurotoxicity • Shock

The Case of the Concerned Citizen• A guy on I-17

The Alleged Scene

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Venomous Lizards

Heloderma suspectumGila Monster

Heloderma horridumMexican Beaded Lizard

Helodermatidae

H. s. suspectum

H.s. cinctumH. h. horridum

H. h. exasperatum

H. h. alvarezi

Gila Monster bite

Resulting in allergic rxn

...and tabloid story!

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Gila Monster Distribution

Reticulated Gila MonsterH. s. suspectum

Banded Gila MonsterH. s. cinctum

Gila MonsterVenom Delivery

• Venom glands on mandible

• Ducts lead to labial mucosa

• Venom flows through grooved teeth and into wounds

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Removing a Gila Monster• Pry mouth apart with pliers• Jam screwdriver down monster’s throat• Dip monster in gasoline and set on fire• Pour gasoline into mouth and set on fire• Place fire under jaw without gasoline• Strike back of lizard’s head with large

stone

Scorpions• 40 species of scorpions in the US• Only one dangerous, considered to

be potentially fatal– Found in Arizona, some areas of

Texas, New Mexico, California, and Nevada

• >6000 calls/year to Samaritan Regional Poison Control Center

• Most managed at home

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The Bark Scorpion

• Centruroides sculpturatus/exilicauda– Yellow/tan/brown– Up to 5 cm in length– Hard exoskeleton– Segmented tail curves up, ends in a

telson, containing venom glands and stinger

Exoskeleton

Telson

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The Bark Scorpion• Body fluoresces under UV light• Resides in or near trees; wood

–Climbs, but not up glass

Bark Scorpion

Envenomation• Most stings cause only local pain • Onset of symptoms immediate, progress up to 5

hours• Children tend to be most severely affected• No deaths reported in the US since 1968

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Management• Most symptoms improve within 9 to

30 hours without treatment• Pain and paresthesias may last up

to 2 weeks• Options:

–Antivenin (not currently available)–Sedation and pain control

Antivenin

• Recommended for Grade III and IV envenomations

• Results in rapid reversal of neurologic and respiratory toxicity within one hour

• Risks– Hypersensitivity reactions– Serum sickness

Scorpion Antivenin

• Goat serum derived• Contraindications

–Previous scorpion antivenin–Asthma–Beta Blockers–CAD

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Black Widow

• Latrodectus mactans• Female is 8-10 mm, black

with red hourglass mark on ventral surface

• Live in woodpiles, crevices, barns…

Envenomation• Female bite produces

sharp pain• Pair of fang marks with

surrounding erythema• 15 minutes to 6 hours

following the bite, “latrodectism”

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Venom

• a-latrotoxin– Potent neurotoxin– Induces neurotransmitter release

from nerve terminals

Latrodectism– Neuromuscular

• Muscle cramps – site, chest, abdomen (may mimic acute abdomen), thighs

• Rigidity, tremor, weakness, priapism

– Systemic • Nausea, diaphoresis,

pavor mortis (fear of death), salivation, urinary retention

– Cardiopulmonary• Hypertension, tachycardia,

bronchorrhea

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Management• Airway • Tetanus

prophylaxis• Pain control • Antivenin to speed

recovery

Management• Airway • Tetanus prophylaxis• Pain control • Antivenin to speed recovery

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